The specificity of lipase for a substrate can be advantageously utilized for an interesterification reaction.
It is considerd that lipase essentially reacts at the interface between water and a lipid. Therefore, probably, because of the fact that the solubility of water in a fat or oil is about 0.2%, an interesterification reaction is often carried out in the presence of a certain amount of water to activate the enzyme, i.e. not less than 0.2% of water based on the substrate (see, for example, Japanese Patent Kokai No. 52-104506). However, in a reaction system containing such water, difficulties such as formation of a large amount of diglycerides are encountered.
The assignee company's Japanese Patent Kokai No. 56-127/087 discloses process for preparing an enzyme preparation having high interesterification activity even in the presence of much less water and, in the extreme case, even in a reaction system from which moisture of a substrate is removed as much as possible in an industrial scale.